I am trying to add two objects to my array but when i inspect the array, the second object appears in the list twice. Does anyone know why?
list = [[NSMutableArray alloc] init];
Person *person = [[Person alloc] init];
// Create person 1
person.name = @"Fred";
person.gender = @"unknown";
// Append to array
[list addObject:person];
[person release];
// Create person 2
person.name = @"Bob";
person.gender = @"male";
// Append to array again
[list addObject:person];
[person release];
You're not creating two person instances, but just one.
Either do this:
list = [[NSMutableArray alloc] init];
Person *person;
// Create person 1
person = [[Person alloc] init];
person.name = @"Fred";
person.gender = @"unknown";
// Append to array
[list addObject:person];
[person release];
// Create person 2
person = [[Person alloc] init]; //this line right here!
person.name = @"Bob";
person.gender = @"male";
// Append to array again
[list addObject:person];
[person release];
or assign a second person to a second variable.
The person variable still points to the first person instance. You need to change the variable to a new instance, otherwise you're simply inserting the person twice and also overwriting its properties.
Redefinition of 'person'
Person * for the second line.Person * part is the definition. The person = …; part is the assignment. You can either combine them into one expression or split them up (as I did. Not necessary though, just clearer, imho).The problem is that the array does not make a copy of the object you passed to it to add, instead it only holds a reference to the object. So what you're doing is creating an object, assigning to its properties, giving a reference to the array, mutating the same object, and then adding the same (but mutated) object to the array again.
You need to make a new Person object each time instead of mutating the same object.
You've only created one person. Try this:
list = [[NSMutableArray alloc] init];
Person *person = [[Person alloc] init];
// Create person 1
person.name = @"Fred";
person.gender = @"unknown";
// Append to array
[list addObject:person];
[person release];
// Create person 2
Person *person2 = [[Person alloc] init];
person2.name = @"Bob";
person2.gender = @"male";
// Append to array again
[list addObject:person2];
[person release];
The issue here is that when you added the first person to the array, and then modified the original object, the object is also modified in the array --- you need to instantiate a new version of the "person" object and modify it.
If you want to create many, many people, I suggest using a for loop:
NSArray *names = [NSArray arrayWithObjects:@"Fred", @"Bob"];
NSArray *genders = [NSArray arrayWithObjects:@"unknown", @"male"];
for (int i = 0; i<[names count]; i++) {
Person *person = [[Person alloc] init];
person.name = [names objectAtIndex:i];
person.gender = [genders objectAtIndex:i];
[list addObject:person];
[person release];
}
Person variables?